Nowadays the use of laundry washing machines, both “simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.
In the present description the term “laundry washing machine” will refer to both simple laundry washing machines and laundry washing-drying machines.
Laundry washing machines generally comprise an external casing provided with a washing tub inside which there is a rotatable perforated drum in which the laundry is placed.
A loading/unloading door ensures access to the tub and the drum.
Laundry washing machines typically comprise a detergent supply unit and a water inlet circuit for the introduction of water and washing/rinsing products (i.e. detergent, softener, etc.) into the tub.
Known laundry washing machines are also provided with water draining devices that may operate both during the initial phases of the washing cycle and at the end of the same to drain the dirty water.
In particular, a known complete washing cycle typically includes a first laundry wetting phase with addition of the washing detergent, a second washing phase during which the tub is rotated and the water contained therein is heated to predetermined temperature values based on the washing programme selected by the user, and a final rinsing and spinning phase.
According to the known technique, the initial wetting phase includes the step of mixing a predetermined amount of detergent with water to form a liquor which is introduced in the tub for wetting the laundry.
A wetting method belonging to the known technique is disclosed in document U.S. Pat. No. 4,489,455A. In this document the wetting phase includes first the preparation of a wash liquor in a wash liquor reservoir. The liquor is prepared by introducing in the wash liquor reservoir a predetermined amount of detergent composition, which may be in granular, paste, gel or in liquid form, and a predetermined amount of water. A proper mixing of the detergent and of the water takes place in the reservoir by the recirculation of the liquid from the bottom of the reservoir back into the reservoir through connecting lines.
Recirculation of the liquid is carried out until the detergent composition is substantially dissolved or dispersed in the water.
The liquor is then distributed by means of a high pressure spray nozzle as the drum rotates and the laundry is distributed about the periphery of the movable drum.
To further enhance distribution of the detergent, wash liquor application may be carried out in several stages, with the drum being momentarily stopped and restarted between each stage to allow the articles to completely redistribute themselves prior to each stage of wash liquor application. Also, multiple spray nozzles may be employed.
However, the method of wetting the laundry above described belonging to the known art poses some drawbacks.
A first drawback posed by this known technique is constituted by the fact that part of the liquor which is sprayed on the laundry falls down in the hollow space between the drum and the tub so that part of the detergent does not reach the laundry. Therefore a perfect and homogeneous distribution of the detergent on the laundry is not guaranteed.
A further drawback of the known technique is presented by the fact that the optimum laundry/detergent ratio is not obtained.
Another drawback is presented by the fact that the distribution phase of the liquor requires rotations of the drum with the laundry placed therein which leads to a high electric power consumption.